IMAGING DIAGNOSIS-SPONTANEOUS PNEUMOMEDIASTINUM SECONDARY TO PRIMARY PULMONARY PATHOLOGY IN A DALMATIAN DOG

Spontaneous pulmonary interstitial emphysema, pneumomediastinum and cervical subcutaneous emphysema secondary to the Macklin effect in dogs with no clinical signs: 12 cases

Pneumomediastinum denotes the presence of gas within the mediastinum and generally occurs by leakage of air from an aerated viscus that traverses or abuts the mediastinal plane. The Macklin effect has been described in several veterinary studies and describes gas tracking along the perivascular interstitium following alveolar rupture causing interstitial emphysema, pneumomediastinum and subsequently cervical subcutaneous emphysema. This retrospective case series describes incidental spontaneous pulmonary interstitial emphysema, pneumomediastinum and cervical subcutaneous emphysema secondary to the Macklin effect in dogs with no related clinical signs. Twelve dogs were identified from the author's institution, of which 75% were Sighthounds (Greyhounds, Whippets or Lurchers). Pulmonary interstitial emphysema had a predominantly paravascular distribution, although in some cases a parabronchial distribution was also identified. We conclude that incidental pulmonary interstitial emphysema, pneumomediastinum and secondary cervical subcutaneous emphysema can be incidental, presumed secondary to the Macklin effect and that Sighthound breeds may be overrepresented.

Air leak syndrome in animals: definition and pathogenesis

Air leak syndrome (ALS) is described in human medicine as a constellation of clinical disorders including pneumomediastinum, pneumopericardium, pulmonary interstitial emphysema, pneumothorax, pneumoperitoneum, pneumoretroperitoneum and subcutaneous emphysema. The pathogenesis of ALS depends on the anatomy of the mediastinum and its associations with thoracic, abdominal and cervical connective tissues, as well as a physical phenomenon referred to as the Macklin effect. Various animal species develop diverse combinations of these lesions, although ALS has not been recognized in animals. However, this term aids pathologists in addressing this disease compilation. The aim of this retrospective study is to illustrate examples of ALS in animals by arbitrarily selecting 13 cases in dogs, cats, pinnipeds, sea otters and harbour porpoises. ALS can be classified into three groups based on aetiology: iatrogenic, secondary or spontaneous. Iatrogenic ALS was diagnosed in two cats with tracheal laceration following endotracheal intubation. Secondary ALS was identified in two dogs, one with acute respiratory distress syndrome and the other due to grass awn migration. Secondary ALS in pinnipeds was diagnosed following severe pulmonary parasitism, uraemic pneumonia and oesophageal perforation. The other marine mammals developed ALS following trauma. Spontaneous ALS was also diagnosed in one cat and one dog without any apparent predisposing causes.

Pulmonary interstitial emphysema and spontaneous pneumomediastinum are more prevalent in sighthounds than other dog breeds undergoing thoracic CT

Spontaneous pneumomediastinum is an uncommon condition described in veterinary medicine with concurrent respiratory disease. It can be caused by the Macklin effect, which is when gas leaks from the alveoli into the surrounding interstitial lung tissue. Pulmonary interstitial emphysema (PIE) is the presence of gas within the pulmonary vascular sheaths and indicates the presence of the Macklin effect. In the authors' experience, spontaneous pneumomediastinum and PIE are more prevalent in sighthound dogs than in other breeds and are often considered incidental findings. This retrospective, observational, cross-sectional study compared the prevalence of PIE and subsequent pneumomediastinum in sighthound with other purebred dogs. It characterized the appearance of PIE in CT and analyzed a possible association with concomitant pulmonary pathologies or with the use of general anesthesia. Medical records and thoracic CTs of sighthounds and nonsighthound dogs from two institutions were reviewed. A total of 256 dogs, comprising 127 sighthounds and 129 other purebred dogs, were included. The prevalence of PIE and pneumomediastinum was statistically higher in sighthound (14.2%) compared with other nonsighthound dogs (2.2%). There was no statistical association between the presence of PIE and pneumomediastinum with different age and weight groups or with sex. There was no statistical difference in the prevalence of PIE and pneumomediastinum between dogs with and without pulmonary pathology or in dogs undergoing CT with sedation or general anesthesia. Spontaneous pneumomediastinum in sighthounds is more prevalent than in other breeds, and its prevalence is not associated with the presence of pulmonary pathology or the use of general anesthesia.

Point-of-Care Ultrasonography Helped to Rapidly Detect Pneumomediastinum in a Vomiting Female

Vomiting-induced pneumomediastinum is a rare presentation and can be a result of alveolar rupture (Mackler effect) or Boerhaave syndrome. Patients diagnosed with Boerhaave syndrome may present with the classic Mackler triad of vomiting, chest pain, and subcutaneous emphysema. However, there exists a large overlap of symptoms accompanying Boerhaave syndrome and the Macklin effect, including retrosternal chest pain, neck discomfort, cough, sore throat, dysphagia, dysphonia, and dyspnea. Boerhaave syndrome is a dangerous condition. Delayed diagnosis of Boerhaave syndrome may worsen sepsis and cause mortality. Therefore, early diagnosis and timely management are important to prevent further complications. Here, we present a case of vomiting-induced pneumomediastinum, which supports the use of bedside ultrasonography to aid in the diagnosis and rapid differentiation of etiology of pneumomediastinum.

Risk factors for mediastinitis and mortality in pneumomediastinum

Introduction: Pneumomediastinum (PM) is a self-limiting disease with a good prognosis. Mediastinitis is a rare but potentially fatal complication of PM. Identification of risk factors for mediastinitis is essential for better management. Methods: This is a single-center, retrospective study conducted in a university hospital. Adult patients with PM between January 2016 and June 2020 were involved in the study. The data about age, gender, symptoms, signs, treatment, development of mediastinitis, hospital stay, and mortality were investigated. Results: In total, 79 patients with PM were analyzed. The most common symptom was dyspnea(58;73.4%) and the most common sign was subcutaneous emphysema (48;60.7%). Thirty(37.9%) of them were iatrogenic PM (IPM), while 22 (27.9%) were spontaneous PM (SPM) and27 (34.2%) were traumatic PM (TPM). Mediastinitis developed in 17 (12 from IPM, 4 from TPM,1 from SPM) patients, and 11 (58.8%) of these patients died. The incidence of mediastinitis in the IPM group was significantly higher than in the TPM and SPM group (respectively, P=0,03,P=0,01). There was no significant difference between the age, gender, symptoms, and signs of those with or without mediastinitis. Mortality was lower in TPM and SPM than IPM (respectively,P=0,05, P=0,03), and hematological malignancy was remarkably common in patients who died from mediastinitis in the TPM and SPM group. Conclusion: Mediastinitis and mortality were significantly higher in IPM, while hematological malignancy was remarkably prevalent in patients deceased from mediastinitis in TPM and SPM.

A Case Series of Secondary Spontaneous Pneumomediastinum and Pneumothorax in Severe COVID-19 Pneumonia

Introduction

Pneumomediastinum and pneumothorax are uncommon complications in COVID-19 patients. The exact prevalence, etiology, and outcomes are not well known. We report a case series of patients in our institution with COVID-19 related pneumomediastinum and pneumothorax and address these questions.

Methods

We conducted a single-center retrospective chart review of patients admitted at our institution with a positive polymerase chain reaction (PCR) confirming the diagnosis of COVID-19. A cohort of 500 potential study candidates was identified, of whom eight were investigated. Demographic data, hospital course, patient co-morbidities, and outcome data were collected.

Results

Eight patients were included in our study who were identified as having an event (i.e., pneumomediastinum and/or pneumothorax) during the specified timeframe. Overall, 62% of patients were on high-flow nasal cannula with an average FiO₂ of >70%. The average oxygen saturation//fraction of inspired oxygen (SpO₂/FiO₂) ratio leading up to an event was 113.7286 (range: 101.11-130.66), and all of the patients not on mechanical ventilation met the criteria for acute respiratory distress syndrome (ARDS) based on the Kigali definition with SpO₂/FiO₂ < 315. The three patients who developed an event while requiring mechanical ventilation both had PaO₂/FiO₂ < 100, consistent with severe ARDS at the time of an event. The mean time in days, counted from the day of hospital admission until an event, was 10 days (range: 3-23 days). None of the cases had documented pulmonary parenchymal disease prior to developing COVID-19. To the best of our knowledge, these events were not iatrogenic in nature.

Conclusion

Secondary spontaneous pneumomediastinum and pneumothorax are rare albeit well-documented phenomena in hospitalized patients with COVID-19 infection. Interestingly, the majority of patients in our study were on high-flow nasal cannula at the time of an event. The majority of previously published data on this topic are on those who required positive pressure ventilation; however, there have been more recent papers that also describe these events in non-mechanically ventilated patients. The exact pathophysiology remains unknown, but it is likely multifactorial, and additional studies are needed to further evaluate this phenomenon.

Pneumoperitoneum as an uncommon complication after an axillary laceration in a horse

Lacerations of the axillary region occur frequently in horses. Typical complications caused by entrapment of air in the wound during locomotion are subcutaneous emphysema, with consecutive pneumomediastinum and pneumothorax. In this case report, the clinical, radiographic and laboratory diagnosis and management of these complications after an axillary laceration that finally resulted in pneumoperitoneum are described. A 1-year-old Hannoveranian was presented with a pre-existing axillary laceration of unknown duration and subcutaneous emphysema in the surrounding tissue. Due to extensive tissue loss, attempts to adequately close the wound surgically and by packing with sterile dressing material were unsuccessful. Despite stall confinement and tying of the horse, subcutaneous emphysema was progressive and pneumomediastinum as well as pneumothorax was developed. These complications were monitored radiographically. On day 5 after admission, signs of air accumulation were detected on radiographs craniodorsally in the peritoneum and a pneumoperitoneum was diagnosed. Repeated thoracentesis with a teat cannula to gradually evacuate the thoracic cavity was used in combination with nasal oxygen insufflation to treat global respiratory insufficiency. Subcutaneous emphysema and all other complications resolved progressively and the horse was discharged from the hospital 21 days after admission when the axillary wound was adequately filled with granulation tissue. The wound healed fully 1 month later and the horse did not develop long-term complications within the following year. To the authors´ knowledge, the development of pneumoperitoneum including its radiographic monitoring following an axillary laceration has not been described in horses previously.

Pneumomediastinum in a cannabis smoker precipitated by vigorous sexual intercourse

Primary pneumomediastinum is the presence of air in the interstitium of the mediastinum. The exact aetiology is unclear; nevertheless, it has been reported more frequently in patients with asthma and in individuals who use recreational drugs. It is commonly preceded by a sharp rise in intrathoracic pressure as in a Valsalva-like manoeuvre. We describe a rare case of severe pneumomediastinum with a small pneumothorax related to cannabis smoking and aggravated by vigorous sexual intercourse. The patient was successfully treated conservatively due to clinical and radiological stability and the absence of secondary cause.

Thoracic radiographic features of fatal paraquat intoxication in eleven dogs

BACKGROUND

Paraquat (1,1-dimethyl-4,4-bipyridinium dichloride) is a toxic herbicide. Accidental ingestion of paraquat in animals and humans causes respiratory failure and death.

AIM

To describe the radiographic features of confirmed paraquat intoxication in a group of dogs and determines whether any identified features can facilitate this diagnosis.

METHODS

Eleven dogs diagnosed with paraquat intoxication were selected from two institutions between November 2014 and August 2019 comprising five males (all intact) and six females (one intact and five spayed). The mean age was 3.9 ± 2.9 (SD) years and their mean weight was 11.6 ± 5.0 kg. The tentative diagnosis was confirmed through analysis of their urine samples using a colorimetric assay (paraquat concentation 0.39 μg/ml ranging from 0.19-0.65 μg/ml), and their clinical signs were reviewed. Thoracic radiographs were evaluated for the presence of pneumomediastinum, lung patterns (interstitial or alveolar) and their locations (caudodorsal, cranioventral, diffuse, or symmetrical), subcutaneous emphysema, pneumoretroperitoneum, and pneumothorax.

RESULTS

The most common clinical signs were dyspnea (11/11, 100%) and anorexia (9/11, 82%). Pneumomediastinum (10/11, 91%) and symmetrically increased lung opacity (7/11, 65%) were the most common radiographic features. Pneumothorax (3/11, 27%), pleural effusion (3/11, 27%), subcutaneous emphysema (2/11, 18%), and pneumoretroperitoneum (1/5, 20%) were the less common findings. None of the dogs survived.

CONCLUSION

Pneumomediastinum and diffuse or symmetrical interstitial or alveolar lung patterns are the most common radiographic features in dogs with paraquat intoxication.

CLINICAL RELEVANCE

In countries where this herbicide is not banned, paraquat intoxication should be considered if dogs with no history of trauma present with pneumomediastinum.

A Rare Presentation of Asymptomatic Spontaneous Pneumomediastinum

Spontaneous pneumomediastinum is a rare condition characterized by interstitial air within the mediastinum without any obvious causative factors. It is most commonly found in young men, and the clinical presentation is typically associated with chest or neck pain and dyspnea. Objective findings can include subcutaneous emphysema of the neck and chest. Asymptomatic cases are exceedingly rare. In this report, we present the case of a 20-year-old woman who presented with acute psychosis and the incidental imaging finding of pneumomediastinum without any associated clinical signs or symptoms.

Spontaneous pneumomediastinum, pneumothorax and subcutaneous emphysema in COVID-19 pneumonia: a rare case and literature review

Spontaneous pneumomediastinum (SPM) and pneumothorax (PNX) unrelated to positive pressure ventilation has been recently reported as an unusual complication in cases of severe COVID-19 pneumonia. The presumed pathophysiological mechanism is diffuse alveolar injury leading to alveolar rupture and air leak. We present a case of COVID-19 pneumonia complicated on day 13 post admission by SPM, PNX and subcutaneous emphysema in a patient with no identifiable risk factors for such complication. The patient received medical treatment for his COVID-19 infection without the use of an invasive or non-invasive ventilator. Moreover, he is a non-smoker with no lung comorbidities and never reported a cough. He was eventually discharged home in stable condition. A comprehensive literature review revealed 15 cases of SPM developing in patients with COVID-19 pneumonia.

Pneumomediastino, pneumotórax e enfisema subcutâneo em cão com pneumopatia e infecção pelo vírus da cinomose: relato de caso

RESUMO Relata-se um caso de pneumomediastino, pneumotórax e enfisema subcutâneo em um cão com pneumopatia associada à cinomose. As queixas principais eram tosse, secreção nasal purulenta, apatia e enfisema subcutâneo em face, região cervical e torácica. O exame radiográfico evidenciou pneumomediastino, pneumotórax e broncopneumopatia grave com áreas de consolidação pulmonar. Teste rápido imunocromatográfico para detecção de antígeno da cinomose foi positivo e houve melhora dos sinais respiratórios com antibioticoterapia, porém o quadro evoluiu para alterações neurológicas. De acordo com a revisão de literatura realizada, não há casos semelhantes relatados.

Pneumocystis carinii infection with severe pneumomediastinum and lymph node involvement in a Whippet mixed-breed dog

A 3.5-y-old Whippet mixed-breed dog was presented with a history of respiratory distress, exercise intolerance, and generalized demodicosis. Hematologic alterations included marked leukocytosis and neutrophilia. Radiographic examination showed a diffuse interstitial and mild peripheral alveolar lung pattern and pneumomediastinum. Because the cytologic examination of the bronchoalveolar aspirate was not diagnostic and a persistent perforation of the upper respiratory tract could not be ruled out, the dog was submitted to thoracoscopy, and subsequently the left cranial lung lobe as well as mediastinal and sternal lymph nodes were resected. Pulmonary pneumocystosis with spread to the thoracic lymph nodes was suspected after histologic investigation of lung and lymph nodes, which was confirmed by in situ hybridization, PCR, and subsequent Sanger sequencing. We document a rare, simultaneous occurrence of severe pulmonary and thoracic lymph node pneumocystosis with spontaneous pneumomediastinum in a dog. Definitive diagnosis was achieved through the use of Grocott methenamine silver staining, in situ hybridization, and PCR.

Pneumomediastinum

Pneumomediastinum is a condition in which air is present in the mediastinum. This condition can result from physical trauma or other situations that lead to air escaping from the lungs, airways or bowel into the chest cavity. Pneumomediastinum is a rare situation and occurs when air leaks into the mediastinum. The diagnosis can be confirmed via chest X-ray or CT scanning of the thorax. The main symptom is usually severe central chest pain. Other symptoms include laboured breathing, voice distortion (as with helium) and subcutaneous emphysema, specifically affecting the face, neck, and chest. Pneumomediastinum can also be characterized by the shortness of breath that is typical of a respiratory system problem. It is often recognized on auscultation by a "crunching" sound timed with the cardiac cycle (Hamman's crunch). Pnemomediastinum may also present with symptoms mimicking cardiac tamponade as a result of the increased intrapulmonary pressure on venous flow to the heart. The tissues in the mediastinum will slowly resorb the air in the cavity so most pneumomediastinums are treated conservatively.